use strict;
use warnings;

package Invoker;

sub first_callback {
   my $z = shift;
   print "in first_callback, z=$z\n";
   return 1;
}

sub last_callback {
   my $z = shift;
   print "in last_callback, z=$z\n";
   return 2;
}

sub invoker
{
   my ($name, $z) = @_;
   my $handler = $name . '_callback';
   no strict 'refs';
   exists(${__PACKAGE__.'::'}{$handler}) or return -1;
   &$handler($z);
}

package main;

# Main program for testing ---------------------------------

for my $name ( "first", "last", "fred" ) {
   my $rc = Invoker::invoker( $name, $name . '-arg' );
   print "$name: rc=$rc\n";
}